Air conditioner employing an expansion evaporation air cycle



H. R. SCHELP Jan. 17, 1956 AIR CONDITIONER EMPLOYING AN EXPANSION EVAPORATION AIR CYCLE 4 Sheets-Sheet 1 Filed Oct. 14, 1949 DBYBULB [IA/D WET BULB WEBMGVEI'EKS INVENTOR.

P M a M; fi 5 T E /fiv W m 5% Jan. 17, 1956 H. R. SCHELP 2,730,874

AIR CONDITIONER EMPLOYING AN EXPANSION EVAPORATION AIR CYCLE Filed Oct. 14, 1949 4 Sheets-Sheet 2 o".-'. 53 INVEN TOR. HELMl/T E 50/161,

Jim-744; BY 451% H. R. SCHEL P Jan. 17, 1956 AIR CONDITIONER EMPLOYING AN EXPANSION EVAPORATION AIR CYCLE 4 Sheets-Sheet 3 Filed Oct. 14, 1949 JUPPLY INVENTOR. HEL/VUT f. JCWELP BY (Um A A W 7r e/vsy M 93.

United States Patent AIR CONDITIONER EMPLOYING AN EXPANSION EVAPORATION AIR CYCLE I- Ielmut R. Schelp, Dayton, Ohio, assignor to The Garrett Corporation, a corporation of California Application October 14, 1949, Serial No. 121,436 14 Claims. (Cl. 62-138) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without the payment to me of any royalty thereon.

The present invention relates to an air conditioning apparatus employing an expansion evaporation air cycle.

The primary object of the invention is to provide a system of air conditioning including a working air cycle which takes advantage of expansion for initial cooling of the working air and which further takes advantage of evaporative cooling as the working air passes through a heat exchanger to avoid any appreciable temperature increase of the working air during the heat transfer phase.

A further object of the invention is to provide a system of air conditioning in which a working air path includes an expansion device near the air inlet, water sprays before, within or after the expansion device, a heat exchanger after the expansion device and a suction device after the heat exchanger to maintain a partial vacuum between the expansion and suction devices, and in which a conditioning air path includes the heat exchanger, suitable ducting and means to cause movement of conditioning air in desired volume for proper ventilation and cooling of a room or other space.

Another object of the invention is to provide a system of air conditioning in which a working air path includes an expansion turbine near the air inlet, water sprays before the expansion turbine, a heat exchanger after the expansion turbine and a suction blower deriving part of its power requirements from the expansion turbine and acting to draw the working air through the expansion turbine and heat exchanger and to maintain sub-atmospheric pressure between the expansion turbine and suction blower, and in which a conditioning air path includes the heat exchanger, suitable ducting and means to cause movement of conditioning air in desired volume for proper ventilation and cooling of a room or other space.

Another object of the invention is to provide a system of air conditioning in which a working air path includes an expansion turbine near the air inlet, water sprays before and after the expansion turbine, a heat exchanger after the expansion turbine, an air compressor after the heat exchanger to maintain a partial vacuum between the expansion turbine and air compressor, a combustion chamber after the air compressor to provide for an increase in volume of the working air flow, a second expansion turbine for operation by the increased volume of air and combustion products and means to utilize power produced by the two expansion turbines in driving the air compressor.

The above and other objects of the invention will become apparent upon reading the following detailed escription on conjunction with the accompanying drawings, in which:

Fig. 1 is a schematic diagram in central cross section of an air conditioner in one preferred form of the invention.

2,730,874 Patented Jan. 17, 1956 ICC Fig. 2 is a schematic diagram in cross section of an air conditioner including an expansion device and jet pump, instead of an expansion turbine and suction blower as shown in Fig. 1.

Fig. 3 is a schematic diagram in cross section of an air conditioner including a Ranque tube coupled with an evaporative cooling chamber.

Fig. 3a is a cross sectional view taken on line a--a of Fig. 3.

Fig. 4 is a schematic diagram in cross section of an air conditioner including a Ranque tube and a double jet pump.

Fig. 5 is schematic diagram in cross section of an air conditioning system for use in large installations where a number of different rooms or spaces are to be cooled or air conditioned.

Fig. 6 is a schematic diagram in cross section of an air conditioning system for use in large installations and differing from Fig. 5 in the omission of a suction blower and the use of the expansion turbine to drive a fluid circulating pump.

Fig. 7 is a schematic diagram in cross section of an air conditioner employing two expansion turbines and a coupled air compressor.

Fig. 7a is a gas pressure diagram to show the relative pressure values through the apparatus of Fig. 7.

Fig. 8 is a schematic diagram in cross section of an air conditioner similar to that of Fig. 7 but including an air selector valve at the inlet side of the first expansion turbine.

Air cycles for use in refrigeration and air conditioning have previously been proposed and have achieved considerable success in special cases, particularly in aircraftcarried cabin conditioners. For instance a discussion of some applications of the air cycle and the theories involved may be found in the July 194-8 issue of the Journal of the A. S. R. E. on pages 53 to 59. Other proposed systems are disclosed in U. S. Patent No. 2,073,833 granted March 16, 1937, to G. De Bothezat, U. S. Patents No. 2,175,162 and No. 2,175,163 granted October 3, 1939, to R. W. Waterfill and U. S. Patent No. 2,453,923 granted November 16, 1948, to A. M. Mayo. The present invention embracing a number of specific embodiments of air cycle systems takes advantage of evaporative cooling and also the cooling elfect obtained in expanding air through an expansion turbine or expansion nozzle. In general the systems disclosed include two separate air flow paths, namely the working air flow path and the conditioning air flow path. The working air flow enters the apparatus at atmospheric pressure but by reason of a suction device near the air outlet the pressure within the apparatus is below atmosphere. Thus the system used may be termed an expansion evaporation vacuum air cycle, because the Working air path is at a partial vacuum during a substantial portion thereof. By providing an expansion device such as an expansion turbine near the inlet end of the working air path, a pressure drop thereacross causes the air to be expanded and cooled because of the loss of kinetic energy and at the same time the energy given up by the air may perform useful work in driving the expansion turbine. Before, during or after the air expansion phase, Water or other liquid is sprayed into the Working air in the form of a fine mist and the intimate contact of air and water provides further cooling of the air by evaporative cooling. As the working air proceeds through a heat exchanger to provide for cooling of the conditioning air it becomes progressively warmer. Each increment of temperature increase causes further evaporation of water or other liquid evaporant and this action in turn extracts heat from the working air, thus tending to maintain the working air temperature constant though the heat exchange phase of the air cycle. Some additional moisture is evaporated in passing'through the suction device, thus reducing the power consumed thereby. Just enough water or liquid is sprayed into the working air to result in complete saturation thereof by the time the air how. is leaving the suction device. Any excess will increase the mass of flowing air and cause the suction device near the outlet end of the working air path to consume more power in drawing a vacuum. By the same token water or liquid sprayed into the working air before it enters the expansion turbine will result in more power output from the turbine and will also permit more time of contact between the air and liquid to provide for more eificient cycle operation. There being eight difierent embodiments of the invention shown in the drawings, the following description is subdivided accordingly in order to make the disclosure proceed in an orderly fashion.

Air cycle system of Fig. 1

In Fig. 1 there is shown a preferred air cycle system wherein the working air path includes an expansion turbine 1 and a suction blower 2. connected by conduits 3 and a heat .exchanger 4. The working air flow enters the apparatus by a conduit 5 and leaves by a conduit 6, from which it is discharged to the atmosphere. The working air entering at conduit 5 will ordinarily be from the free atmosphere or from the room being air con ditioned. Upstream of expansion turbine i is a water spray nozzle 7 connected to a pump 8 and a supply of water 9. The turbine 1 and blower or compressor 2 are interconnected by a drive shaft it from which power may be taken to drive a fan 11 for moving the conditioning air flow through duct 12 on its way to the room being air conditioned or cooled. As the air in duct 12 moves in the direction of the arrows it passes around the tubes of heat exchanger 4, which are normally at a lower temperaturethan the conditioning air flow. Thus the air becomes cooled and also loses some of its moisture content by condensation on the cold tubes of the heat exchanger. The drive shaft extends outside the air conditioning apparatus for connection with a prime mover or motor 13. The motor supplies power to assist in driving the fan 11 and the blower 2, although it should be understood that some power is derived from the expansion turbine 1.

The apparatus or system of Fig. 1 operates on what may be termed an expansion evaporation air cycle. The air flow in conduit 5, which is at atmospheric pressure whether it comes from the free atmosphere or from the conditioned room, acts to rotate the impeller of expansion turbine I and thus gives up some of its heat energy thereby cooling down. The exhaust side of turbine 1 is at a negative pressure because of the suction fan or blower 2, and therefore the working air entering at 5 exerts a driving effect on the turbine impeller. Before entering the tun bine, the working air picks up moisture in passing the spray nozzle 7, whereby its mass is increased for greater energy output from the turbine .l. The air carrying excess water over that required for saturation enters the heat exchanger tubes at a temperature determined by the energy extracted in going through the turbine. Also a small temperature decrease may be due to evaporating moisture while moving from the turbine to the heat exchanger. In passing through the heat exchanger the working air becomes warmed up by heat transfer through the tube walls but any increase in temperature enables the working air to evaporate more water thus tending to lower the air temperature. The result is that the tendency to warm up the air by heat transfer is balanced out by loss of heat by evaporation of more water, since as is well known the moisture content of saturated air increases with increase in temperature. The temperature of air entering the heat exchanger is accordingly maintained through the exchanger by reason of the evaporative cooling efiect. Now the air which is still supersaturated fiows to the compressor where work is done on the air tending to increase its temperature. It'is'now capable of evaporating still more moisture and its temperature rise through the compressor is held to a minimum and the work required of the compressor is minimized to some extent. The reason for this is obvious when it is realized that increase in temperature of a working medium, such as a gas or fluid, always means that work is being done to bring about the temperature rise. The water fiowing to spray nozzle 7 may come from a reservoir 9 and be pumped by any type of pump 8. The pressure of the watermay be regulated by the pump in order to deliver a controlled volume of water to the working air flow. The ideal situation, and that which dictates the rate of water flow through the spray nozzle 7, is one where the working air leaving the blower or compressor 2 is saturated but carries no excess moisture. In keeping with the foregoing I have shown a regulating handle 8a for the pump P so that it may be adjusted to deliver an amount of water just suflicient to produce total saturation of the working air, as indicated by the thermometric means disposed downstream from the heat exchanger 4. Any increase in moisture content over this ideal amount will tend to increase needless consumption of water. blower 2 the pressure of the working air is boosted to slightly above atmospheric and then the air is discharged by conduit 6 to the ambient atmosphere. From the above explanation it will be seen that the cooling of the working air through the apparatus is due to extraction of heat energy in the expansion turbine l and to the extraction of heat energy by evaporation of moisture from the water sprayed through the nozzle 7. The room conditioning air passage along duct 12 is cooled and dehumidified by passage over the relatively cold tubes of heat exchanger 4 before being conducted to the room or space to be conditioned. If the working air supply is taken from the conditioned space so that it will be cooler and dryer than outside air, then'it may be desirable to take most of the conditioning air. from the ambient atmosphere. The term air conditioning in the present description implies the cooling and dehumidifying of controlled quantities of air and conduc the air to a room, cabin or space to be air conditioned for increasing the comfort conditions in enclosed spaces during hot weather or to control the air conditions for the benefit of specific processes or manufacturing operations being carried out in enclosed spaces.

Air cycle system of Fig. 2

lever 8a. The moisture laden air flows through the throat 15 and enters the tubes of heat exchanger 17.. In absorbing heat from the tubes the air is able to gradually evaporate more of the excess moisture carried along into the tubes, so that the air temperature tends to be maintained at or near the'level at which it enters the tubes. The fiow of air is maintained by the jet pump 18 which includes a high pressure discharge nozzle 19 discharging high pressure air, gas or steam through a restricted throat in the jet pump. The flow of fluid from the nozzle 19 produces a negative pressure in the conduit 20, thus maintaining working air flow from the space 14 along the path including expansion nozzle 15 and heat exchanger 17. The tubes of heat exchanger 17 are cooled by worki 3 air flow and therefore the conditioning air flow along the mai a duct 20 is cooled and dehumidiiied as it passes around the tubes on the way to the room 14 being air conditioned. Air flow through duct 29 is maintained by a fan 2?. drivenby a Before entering the motor 22 or other power source. The air supply to the duct is provided by an air return duct 23 and a fresh air duct 24, the latter two ducts merging into the main duct 20' as shown. A gate damper 25 may be provided at the merging point of these supply ducts to proportion the return and fresh air flow. Unless the fresh air is exceptionally warm and humid, the amount of fresh air should ordinarily be greater than the return air flow, but it will be seen that too large a proportion of fresh air will impose a larger cooling load on the apparatus.

Air cycle system of Fig. 3

The air cycle system of Fig. 3 includes an application of the Ranque tube in place of an expansion turbine or expansion nozzle. The Ranque tube or Ranque centrifugal jet is a device having no moving parts and comprising a central circular chamber into which air or other gas is made to how tangentially. The chamber is open at each end but one opening is much smaller than the other. The rotating air flowing in the chamber raises the pressure at the tube surfaces and lowers the pressure at the tube axis. Along a radial line there will thus be a pressure drop to cause an adiabatic expansion, leaving hot air at the tube periphery and cold air at the tube axis. The hot air thus flows from the tube opening of larger diameter, while the cold air flows from the tube opening of smaller diameter. The details of construction of the Ranque tube may be found on page 59 of the magazine cited above. in the schematic diagram of Fig. 3 the Ranque I tube is indicated at 26, the smaller axially extending opening at 27 and the larger axially extending opening at 28. The larger opening is extended into an enlarged spray chamber 29 equipped at its upper end with a water spray nozzle 39 from which water is sprayed in a fine mist continually, this water spray nozzle 30 being supplied by a variable flow pump P having a regulating handle 8a. The air supply into the Ranque tube preferably comes by an air return conduit 31. extending from the conditioned room 32. The cold air outlet 27 of the Ranque tube extends to a heat exchanger 33 and the air passing through the exchanger flows to some kind of suction device, such as a suction blower or jet pump. The conditioning air flows along the main duct 34 under the driving action of a fan 35 driven by a motor 36 or any other source of power. The air from the atmosphere is passed over the exchanger tubes where it is cooled and dehumidified before flowing into the room 32. While it is preferred to use room return air or exhaust air as a source of the working air flowing to Ranque tube 26, it is also possible to use atmospheric air instead.

In the system of Fig. 3 the special application of the Ranque tube in an expansion evaporation air cycle is the important feature. The cold air flowing down the smaller central opening27 will have adefinite cooling eliect on the heat exchanger tubes. However, the Warmer air flowing into spray chamber 29 meets the water spray, whereby its temperature is reduced to the wet-bulb temperature. The wet-bulb temperature will depend on the relative humidity of the air entering the Ranque tube along conduit 31, thus it is seen that exhaust air from the room 32 would usually be preferable to outside air for better efficiency. The Warmer air now reduced to the wet-bulb temperature mixes with the colder air leaving the Ranque tube by way of the central opening 27, the mixed air flow moving through the tubes of heat exchanger 33. As the air becomes heated in passing through the tubes it will evaporate more moisture, thus helping to prevent a temperature rise of the air during the tube traverse. The Ranque tube as used in the system of Fig. 3 provides a form of expansion nozzle and in conjunction with the spray chamber 29 and spray nozzle 30 provides a compact and efiicieent arrangement for carrying out some of the functions of the present expansion evaporation air cycle. Since the water spray mixes with the air during its expansion in the Ranque tube, temperature rise in the air moving into the chamber 29 is inhibited and the resulting combined air flow through the reduced central opening is held to a minimum temperature.

Air cycle system of Fig. 4

The air cycle system of Fig. 4 includes another and more elaborate application of the Ranque tube. The Ranque tube is indicated at 26 and extending axially therefrom are the small opening 27 and large opening 28. The large opening 28 merges upwardly into a conduit 49 wherein is located a spray head 30 which receives water under pressure from a variable: pump P having a regulating lever 8a adapted to spray water in a fine mist both upwardly and downwardly. Air is supplied to the Ranque tube by means of a conduit 31 extending from the air conditioned room 32. The smaller air opening 27 from the Ranque tube extends to a heat exchanger 33 mounted in the main air duct 34 through which the conditioning air flows from an outside source. Air flow through the main duct 34 and into the room 32 is maintained by a fan 55 driven by a motor 56 and appropriate gearing as shown. The conduit 49 extends over to a second or auxiliary heat exchanger 57 mounted in the main duct 34. Working air flow from the primary heat exchanger 33 enters a short conduit 58% through which extends a jet pipe 59 carrying high pressure air, engine exhaust gas or steam to provide a jet pump and thus maintain flow through the Ranque tube 26. The conduit 58 terminates in a second jet pipe 61 extending into a conduit 60 from the secondary heat exchanger. The combined fiow from pipe 59 and conduit 58 merge and are blown from the second jet pipe to provide suction on the conduit 49, heat exchanger 57 and conduit 60. The combined flow from the jet pipe 61 and conduit 60 merge and flow into the free atmosphere by way of an outlet pipe 62. The first jet 59 may be termed the high pressure jet and the second jet d1 may be termed the low pressure jet.

In the operation of the system of Fig. 4 the induced air fiow in conduit 31 supplying the working air flow enters the Ranque tube 26 (see Fig. 3a) with a swirling motion and as explained above the cold air at the center is free to flow down the smaller outlet 27. The warmer air layers formed at the outside of the Ranque tube flow upward into the conduit 49 where the warm air meets the water spray from nozzle 30. This air is now reduced to the wet bulb temperature by evaporation of moisture as it passes on toward the secondary heat exchanger 57. The cooled air carries along an excess of free moisture, so that the air during passage through the tubes of the heat exchanger 57 tends to remain cool because increase in temperature enables it to evaporate still more moisture. The conditioning air flowing through the heat exchanger 57 along main duct 34 will be cooled down to some extent before passage to the primary heat exchanger 33. The colder air from Ranque tube 26 flows down the small opening 27 to the tubes of heat exchanger 33 and carries along free moisture, so that in warming up in passing along the tubes the air will evaporate moisture and be maintained at a lower temperature than if the water spray were not present. The conditioning air flow having been cooled in passing the heat exchanger 57, will now be further cooled in passing the heat exchanger 33 before flowing on to the room 32. The speed of the fan 55 should be regulated to provide the proper air changes of the room per unit of time, depending on the type of room being air conditioned.

Air cycle system of Fig. 5

The air cycle system of Fig. 5 is one which is particularly intended for use with a central power plant located at a distance from a plurality of rooms to be air conditioned and at a distance from an equal number of air conditioning units, one of which is shown. The central power plant or the salient parts thereof are indicated at 63, while the air conditioning unit is indicated at 64.

gra ers illhes'e parts are connected by La conduit .65 and other air conditioning units :are connected to the central plant by conduits 66 and 67. 7 These conduits carry portions of the working air flow from the air conditioning units to a suction blower '68oper-ated by aprime mover 69 forming a part of the central power plant.

The air conditioning unit 64 comprises an expansion turbine 70 receiving air at 71 from the outside atmosphere or by return pipe from the room being air conditioned.

. The expansion turbine furnishes power for the suction blower 72 which .e'xhaustsinto the conduit 65, where the pressure is lowered by the .main blower 68. Thus because the blower 72 is exhausting into a space where the air pressure :is negative, the power requirements are light and the expansion turbine 70 will furnish sufficient power for operation of the blower 72. In the air flow path there are provided water spray nozzles 73 downstream of the expansion turbine and at least one nozzle 74 may also be provided upstream of the turbine; if desired, the nozzles 73 and '74 being supplied with water under pressure by a variable pump P having a regulating lever 8a. working airflows from the turbine 70 to the blower 72 byway of a heat exchanger 75located within a main duct 76 carrying the conditioning air flow. The nozzles 73 are positioned so as to direct a water spray into the tubes of the heat exchanger 75. The flow through the duct is maintained by a fan 77 adapted for rotation by means of a motor 78 and associated bevel gearing 79.

The operation of the system of Fig. 5 is similar to that of the others previously described. The induced flow of air into the expansion turbine 70 causes rotation thereof and the work done :by the air in rotating the turbine causes a loss of heat energy, thus cooling the air. Injection of Water into the moving air prevents any appreciable rise l ture rise will cause the air to be at such a temperature that in traversing the relatively iong conduit 65 there will be little heat transfer through the conduit walls. Therefore the branch conduits 65 to 67 will require no insulation to prevent warming up of the air as it passes toward the main blower 68. The air is now passed I through the main blower where its pressure is further increased to slightly above atmospheric, so that it can be ejected into the outside atmosphere.

Air cycle system of Fig. 6

The system of Fig. -6 is similar to Fig. 5 in that it is also suited for use with a large central power plant. The power plant portion of the system is indicated at 83,

while the air conditioning or cooling unit illustrated is indicated at 84. The two parts are connected by a conduit to carry the working air from the air conditioning unit to the central plant and other conduits 86 and '87 carry working air from other conditioning units (not shown) to the central plant. The central plant 83 includes a large size blower 88 for exhausting the working air to the atmosphere and this blower is driven by a prime mover 89 of any desired or convenient type. The air conditioning or cooling unit 84 includes an expansion turbine 90 receiving working air by way of an air intake conduit 91 having located therein a Water spray nozzle 92 which receive water from a variable pump P having a regulating handle 8a. Working air flows from the energy extracting expansion turbine 90 to the heat exchanger 93 andthence into the relatively long conduit 85 The V line .96. The fluid medium circulated by pump 94 may be water for process work for instance. Another application may be in cooling gasoline or other motor fuel subject to rapid-evaporation and fire hazard.

Air-cycle system of Fig. 7

The air cycle system as illustrated in Fig. 7 .is similar in some respects to that of Fig. 1 but embodies a special type of suction blower drive making use of the working air flow. The working air flow enters the apparatus by the suction pipe or conduit and then passes through the expansion turbine 101, where a temperature drop in the air occurs. The air then passes through the heat exchanger 102 mounted in the main air duct 103, and then flows into a self-contained unit 104 combining both a compressor 105 and a combustion gas turbine 106. The unit 104 is enclosed in a cylindrical housing 107 having an open outlet end .108 for the .free discharge of the working air and combustion gases therefrom. A drive shaft 109 connects together the low pressure expansion turbine 101, the compressor 105 and the high pressure combustion turbine 106, whereby power derived from the two turbine components may be used to drive the compressor or blower. Between the outer wall 107 and inner wall 110 of the compressor-turbine unit 104 there is provided an annular combustion chamber 111 wherein is located fuel spray nozzles 112 supplied with liquid fuel from a fuel tank 113. In the air intake conduit 100 is a water spray nozzle 114 and after the expansion turbine, that is downstream thereof and directed into the heat exchanger 102, are other water spray nozzles 115. The spray nozzles 114and 115 are fed with water by a variable pump P having a regulating lever 8a. In order to maintain conditioning air flow in the main air duct 103 there is provided a fan 116 driven by a motor 117 and bevel gearing 113.

The operation of the system of Fig. 7 is a little more involved than the previously described systems. The working air flow first picks up some moisture at the nozzle 114 and then delivers energy to the expansion turbine 101, whereby a substantial temperature drop in the working air occurs. The air then picks up more moisture at the nozzles 115 and passes through the heat exchanger 102 to cool the tubes thereof. As in the other forms of the invention the excess moisture carried over beyond that required to lower-the air temperature to the wet bulb level is useful in maintaining a lower air temperature through the heat exchanger, since a rise in air temperature enables the evaporation of more moisture and a corresponding tendency to lower air temperature. The air now passes to the compressor 105 which functions to maintain air ilow through the expansion turbine 101 and heat exchanger 102, as well as to deliver compressed air to combustion chamber 111. Here the fuel from. the fuel spray nozzles 112 burns with the consequent rapid expansion of air and gases and as a result of the flow of hot gases from the combustion chamber, the turbine 106 is rotated for the delivery of power to the compressor 105. It is understood that the expansionturbine 101 produces power for the compressor operation also but its power output will be smaller than that of the combustion turbine 106. The conditioning air flow through the duct 103 in the direction of the arrows is cooled and dehumidified in passing-over the tubes of the heat exchanger 102 before flowing to the room to be air conditioned.

Attention is further directed to Fig. 7a to show the co nparativc pressure changes through the air cycle system of Fig. 7. Considering the'horizontal base line as atmosheric pressure, the pressure curve first covers part A where pressure is decreasing below atmosphere from the inlet to the outlet of expansion turbine 10-1. This below atmosphere pressure .is produced by the suction effect of compressor 105,.an'd is maintained asthe working air passes through the tubes of heat exchanger 102, that is part B of the 'pressure'curve. "G'ver'part C of the pressure curve the air goes from the negative pressure level to a comparatively high positive pressure level in passing through the compressor 105. This level is maintained fairly constant throughout the combustion chamber 111, as shown by part D of the curve, but in delivering power to turbine ran the pressure is brought back to an atmospheric level for discharge from the turbine tail pipe 108. This pressure drop during power delivery is shown by part E of the pressure curve. The system as shown and described is compact and adapted for many special applications, either large or small in requirements.

Air cycle system of Fig. 8

The system of Fig. 8 is essentially a duplicate of that shown in Fig. 7 but further includes a selector valve 120 for providing three possible variations in the character of the intake air for the expansion turbine 101'. The valve 124) has three inlet openings 121, 122 and 123 connected by conduits to the main air duct 103, to the room 124- and to the outside atmosphere respectively. A rotary element 125 in the valve has a radial passage 126 adapted to be connected to the valve openings 121, 122 or 123 and also in continuous communication with the air supply conduit 1% extending to the expansion turbine 101. The mode of operation of the system is the same as for Fig. 7 but it is now possible to select within limits the air admitted to the working air cycle. If the outside air is comparatively dry and not too hot, the air may then be admitted at valve port 123 for best results and cycle ethciency. However if the outside air is both hot and humid it may be preferable to select the valve port 122, whereby return air from the room 124 may be used in the working air cycle for best efi'ect. When the cooling load is especially severe, the valve port 121 may be selected in order to take the working air directly from the conditioning air duct MP3. The inlet air to the expansion evaporation air cycle will now be as cold and as dry as any available in the apparatus shown and the cooling effect on the heat exchanger will therefore be at a maximum. The rotary element or plug 125 of the air selector valve 120 may be turned by any convenient means, such as a stem and handle projecting from the side opposite to the inlet end of the air supply conduit 1%.

As previously explained the water spray nozzles located upstream, within or downstream of the expansion device should supply just enough water to the working air to result in complete saturation of the air by the time the working air flows from the suction blower, compressor or other suction device into the atmosphere or in the case of the apparatus of Figs. 7 and 8 by the time the working air flows from the air compressor into the combustion chamber. The reasons for this have been stated at some length above. This desirable result may be obtained by temperature determination in the working air stream leaving the blower or compressor and precise adjustment of the water flow rate in accordance therewith. For example in Pig. 1 the blower discharge outlet may have installed therein a dry-bulb thermometer and a wetbulb thermometer. With operating conditions steady the water spray pressure is increased slowly to increase the flow of water through the water spray nozzle 7 until the dry-bulb temperature decreases to the level of the wet-bulb temperature. At this point of adjustment the working air leaving the blower 2 will be saturated but will carry no excess moisture. Another method is to use only the dry-bulb thermometer and slowly increase the flow of water through the spray nozzle 7 until the drybulb temperature recedes to a minimum level. When further increase in the rate of water flow causes no further decrease in dry-bulb temperature, then the operator may be sure that the working air leaving the blower is completely saturated. By careful adjustment of the flow of water through the spray nozzle or nozzles this minimum dry-bulb temperature, which should equal the wet-bulb temperature, may be held within fairly close limits. These same control methods and devices may be used in all Cir 10 embodiments of the invention, that is by temperature adjustment of the working air leaving the blower, compressor or other suction producing device.

The most important advantages of the present air cycle air conditioning system are as follows:

l) The partial vacuum maintained along the working air path together with evaporative cooling of the working air results in low power requirements.

(2) The partial vacuum maintained along the working air path permits more efiicient evaporative cooling of the working air.

(3) The use of water sprays situated directly in the working air flow permits more eflicient and rapid evaporative cooling of the working air.

(4) The use of water sprays within or close to the Ranque tubes in the apparatus of Figs. 3 and 4 provides a compact and effective arrangement for use in an expansion evaporation air cycle.

(5) The use of air for the cooling cycle makes it possible to place an air conditioning unit in a room or other space at any desired location, with only a single pipe connection from the unit at the outlet end of the working air path and extending from the room to the atmosphere or to a central plant as in the apparatus of Figs. 5 and 6. The embodiments of the invention herein shown and described are to be regarded as illustrative only and it is to be understood that the invention is susceptible of variations, modifications and changes within the scope of the appended claims.

I claim:

1. In an air cycle air conditioning system, an expansion turbine including an air inlet for working air at atmospheric pressure and an air outlet to discharge said working air at a reduced temperature and at a pressure below atmosphere after passing through said expansion turbine, nozzle means for introducing a fine spray of water into the working air before its entry into said expansion turbine for evaporative cooling of said working air, a heat exchanger connected to said air outlet and providing a path for said working air after leaving said expansion turbine, a first suction blower for maintaining said working air at a pressure below atmosphere between said expansion turbine and said first suction blower and including an air inlet for the working air leaving said heat exchanger and an air discharge outlet, duct means extending from said air discharge outlet to a central power plant, a second suction blower included in said central power plant and connected to said duct means to maintain said working air at a pressure below atmosphere between said first suction blower and said second suction blower but at a pressure higher than that maintained between said expansion turbine and said first suction blower, means to regulate the flow of water through said nozzle means whereby the moisture content of the working air issuing. from said second suction blower into the atmosphere is capable of regulation to obtain total saturation, duct means to conduct conditioning air through said heat exchanger along a path separate from the working air path but in heat exchange relation with respect thereto, and means to maintain a flow of said conditioning air.

2. In an air cycle air conditioning system as recited in claim 1, power transmission means extending from said expansion turbine to said first suction blower to utilize the power output of said expansion turbine in performing useful work.

3. In an air cycle air conditioning system, an expan sion device including an air inlet for Working air at atmospheric pressure and an air outlet to discharge said working air at a reduced temperature and at a pressure below atmosphere after passing through said expansion device, a first nozzle means for introducing a fine spray of water into the working air before its entry into said expansion device for evaporative cooling of said Working air, a second nozzle means for introducing a fine spray of water into the working air immediately after passing through said expansion device for further evaporative cooling of said working air, a heat exchanger connected to said air outlet and providing a path for said working air after leaving said expansion device and after passing said second nozzle means, a compression device for maintaining said working air at a pressure below atmosphere between said expansion device and said compression device and including an air inlet for the Working air leaving said heat exchanger and an air discharge outlet, means to regulate the flow of water through said first and second nozzle or to obtain total saturation of the working air after passing said second nozzle means, duct means to conduct conditioning air through said heat exchanger along a path sep arate from the working air path but in heat exchange relation with respect thereto, and means to maintain a flow of said conditioning air along said separate path.

4. In an air cycle air conditioning system, an expansion device including an air inlet for working air at atmospheric pressure and an air outlet to discharge said working air at a reduced temperature and at a pressure below atmosphere after passing through said expansion device, nozzle means for introducing a fine spray of water into the working air before its entry into said expansion device, a heat exchanger connected to said air outlet and providing a path for said working air after leaving said expansion device, and nozzle means placed so as to spray water into said heat exchanger, a compression device for maintaining said working air at a pressure below atmosphere between said ex, ansion device and said compression device and including an air inlet for the working air leaving said heat exchanger and an air discharge outlet, duct means to conduct conditioning air through said heat exchanger along a path separate from the Working air path but in heat exchange relation with respect thereto, and means to maintain a flow of said conditioning air alongsaid separate path.

5. in an air cycle air conditioning system, an expansion turcine including an air inlet for working air at atmospheric pressure and an air outlet to discharge said working air at a reduced temperature and at a pressure be ow atmosphere after passing through said expansion nozzle means for introducing fine spray of LilO the working air for evaporative cooling of air and whereby total saturation of the working air obtained after it has passed said nozzle means, a heat exchanger connected to said air outlet and providing a path for said working air after leaving said expansion turoinc and after passing said nozzle means, a first suction blower for maintaining said working air at a pressure lxelow atmosphere between said expansion turbine and said first suction blower and including an air inlet for the working air leaving said heat exchanger and an air discharge outlet, duct means extending from said air discharge outlet to a central power plant, a second suction blower included in central power plant and connected to said duct means to maintain working air at a pressure below atmosphere beveen said first suction blower and said second suction blower but at a "cssure higher than that maintained between said expansion turbine and said first suction blower, duct means con 2t conditioning air through said heat exchanger along a path separate from the working air path but in heat exclnge relation. with respect thereto, and means to rnainLn a flow of said conditioning air along said separate path.

6. in an air cycle air conditioning system, an expansion turbine including an air inlet for working air at atmospheric pressure and an air outlet to discharge said working air at a reduced temperature and at a pressure below atmosphere after passing through said expansion turbine, nozzle means for introducing a fine spray of water into the working air before its entry into said expansion turbine for evaporative cooling of said working air, a heat exchanger connected to said air outlet and providing a path for said working air after leaving said expansion turbine, a first suction blower for maintaining said working air at a pressure below atmosphere between said expansion turbine and said first suction blower and including an air inlet for the working air leaving said heat exchanger and an air discharge outlet, a second suction blower having its inlet connected to the outlet of said first blower for reducing the pressure ratio between the inlet and outlet of said first blower, means to regulate the flow of water through said nozzle means whereby the moisture content of the working air issuing from said second suction blower into the atmosphere is capable of regulation to obtain total saturation, duct means to conduct conditioning air through said heat exchanger along a path separate from the working path but in heat exchange relation with respect thereto, and means to maintain a flow of said conditioning air.

7. An air conditioning system as defined in claim'6 having means for utilizing power developed by said expansion turbine to drive one of said blowers.

8. In an air cycle air conditioning system, an expansion device including an air inlet for working air and an air outlet to discharge said working air at a reduced temperature and at a pressure below atmosphere after passing through said expansion device, nozzle means placed so as to introduce a fine spray of water into the working air upstream from said expansion device so that said spray will pass through said expansion device and saturate said working air, a heat exchanger connected to said air outlet and providing a path for said saturated working air after leaving said expansion device and after passing said nozzle means, a compression device for maintaining the W0 ;ing air at pressure below atmosphere and including an air inlet for the working air leaving said heat exchanger and an air discharge outlet, suction means connected to said air discharge outlet operative to reduce the pressure in the outlet of said compression device, duct means to conduct conditioning air through said heat exchanger along a path separate from the working air path but in heat exchange relation with respect thereto, and means to maintain a flow of said conditioning air along said separate path.

9. In an air cycle air conditioning system, an expansion device including an air inlet for working air at atmospheric pressure and an air outlet to discharge said working air at a reduced temperature and at a pressure below atmosphere after passing through said expansion device, a heat exchanger connected to said air outlet and providing a path for said working air after leaving said expansion device, nozzle means for introducing a fine spray of water into the working air before its entry into said expansion device and nozzle means placed so as to spray water into said heat exchanger, a compression device for maintaining said working air at a pressure below atmosphere between said expansion device and said compression device and including an air inlet for the working air leaving said heat exchanger and an air discharge outlet, suction means connected to said air discharge outlet operative to reduce the pressure in the outlet of said compression device, duct means to conduct conditioning air through said heat exchanger along a path separate from the working air path but in heat exchange relation with respect thereto, and means to maintain a flow of said conditioning air along said separate path.

10. In a method of cooling a fluid wherein it is brought in heat exchange relation to a flow of working air, which is moved through a heat exchanger at least in part by a suction pump connected to the working air outlet of the heat exchanger, the steps of: passing the flow of worl; ing air through an expansion cooling turbine and then through a heat exchanger in heat transfer relation to the fluid which is to be cooled; directing a spray of water into said, flow of working air upstream from the ex pansion turbine to increase the weight-flow through said 13 turbine and cool the water which is entrained in the working air; directing a spray of water into the working air space of said heat exchanger to keep the working air substantially saturated as it passes through the heat exchanger; transmitting power developed by said turbine to said suction pump; and applying suction to the outlet of said suction pump to reduce the pressure ratio against which the suction pump operates.

11. In a method of cooling a fluid wherein it is brought in heat exchange relation to a flow of working air, which is moved through a heat exchanger at least in part by a suction pump connected to the working air outlet of the heat exchanger, the steps of: passing the flow of working air through an expansion cooling turbine and then through a heat exchanger in heat transfer relation to the fluid which is to be cooled; directing a spray of water into said flow of working air upstream from the expansion turbine to increase the weightflow through said turbine and cool the water which is entrained in the working air; directing a spray of water into the working air space of said heat exchanger to keep the working air substantially saturated as it passes through the heat exchanger; connecting a second suction pump to the outlet of said first named suction pump to reduce the pressure ratio against which first named suction pump operates; transmitting power developed by said turbine to said first named suction pump; and applying to said second suction pump power to drive the same.

12. In a method of cooling a fluid wherein it is brought in heat exchange relation to a flow of working air, which is moved through a heat exchanger at least in part by a suction pump connected to the working air outlet of the heat exchanger, the steps of: passing the flow of working air through an expansion cooling turbine and then through a heat exchanger in heat transfer relation to the fluid which is to be cooled; directing a spray of water into said flow of working air upstream from the expansion turbine to increase the weight-flow through said turbine and cool the water which is entrained in the working air; directing a spray of water into the working air space of said heat exchanger to keep the working air substantially saturated as it passes through the heat exchanger; connecting a second suction pump to the outlet of said first named suction pump to reduce the pressure ratio against which first named suction pump operates; transmitting power generated by said turbine to one of said suctionpumps to drive the same; and applying power to the other of said suction pumps to drive it.

13. In a method of cooling a fluid wherein it is brought in heat exchange relation to a flow of working air, which is moved through a heat exchanger at least in part by a suction pump connected to the working air outlet of the heat exchanger, the steps of: passing the flow of working air through an expansion cooling turbine and then through a heat exchanger in heat transfer relation to the fluid which is to be cooled; directing a spray of water into said flow of working air upstream from the expansion turbine to increase the weight-flow through said turbine and cool the water which is entrained in the working air; regulating the amount of water sprayed into said flow of working air so that the working air discharged from said heat exchanger will be substantially saturated; transmitting power developed by said turbine to said suction pump; and applying suction to the outlet of said suction pump to reduce the pressure ratio against which the suction pump operates.

14. In a method of cooling a fluid wherein it is brought in heat exchange relation to a flow of working air, which is moved through a heat exchanger at least in part by a suction pump connected to the working air outlet of the heat exchanger, the steps of: passing the flow of working air through an expansion cooling turbine and then through a heat exchanger in heat transfer relation to the fluid which is to be cooled; spraying water into said How of working air upstream from the outlet of said heat exchanger to substantially saturate the working air during its passage through said heat exchanger; regulating the amount of water sprayed into said flow of working air so that the working air discharged from said heat exchanger will be substantially saturated; transmitting power developed by said turbine to said suction pump; and applying suction to the outlet of said suction pump to reduce the pressure ratio against which the suction pump operates.

References @ited in the file of this patent UNITED STATES PATENTS 1,952,281 Ranque Mar. 27, 1934 2,069,269 Perkins Feb. 2, 1937 2,175,162 Waterfill Oct. 3, 1939 2,175,163 Waterfill Oct. 3, 1939 2,184,613 Evleth Dec. 26, 1939 2,304,151 Crawford Dec. 8, 1942 2,453,923 Mayo Nov. 16, 1948 2,477,931 King Aug. 2, 1949 

